PhenX Toolkit:
|About the Measure |
|Domain |Sickle Cell Disease: Cardiovascular, Pulmonary, and Renal |
|Measure |Liver Iron |
|Definition |A measure to quantify iron in the liver using magnetic resonance imaging (MRI). |
|About the Protocol |
|Description of Protocol |This protocol includes a brief background describing how magnetic resonance imaging (MRI) is used to |
| |determine the concentration of iron in the liver and provides references for quantifying liver iron by |
| |MRI R2*. |
|Protocol text |Description of Quantification of Liver Iron by Magnetic Resonance Imaging (MRI) |
| | |
| |MRI indirectly visualizes iron by imaging water protons as they diffuse near iron deposits. In tissues |
| |with significant iron concentrations, the magnetic iron deposits destroy the homogeneity of the magnetic|
| |field. Water protons moving through these significantly different magnetic profiles become |
| |desynchronized from one another causing the MRI image to darken at a rate proportional to the iron |
| |concentration. |
| | |
| |MRI images for determination of iron content are generated by refocusing the desynchronized water |
| |protons either by a radio-frequency (rf) pulse, termed a spin echo, or by an additional magnetic field |
| |known as a gradient, termed a gradient echo. The longer the echo times (TE), the darker the images. The |
| |decline in image intensity is characterized by a half-life time constant, known as T2 if a spin echo is |
| |used, or T2* if a gradient echo is used. The reciprocal of the time constant, or the rate of image |
| |darkening, is known as R2 (reciprocal of T2) or R2* (reciprocal of T2*). |
| | |
| |Quantifying Liver Iron by MRI R2* |
| |A description of MR studies for the determination of liver R2* can be found in the Methods section of |
| |Garbowski et al., 2014. |
| | |
| |A description of MR studies for determination of R2 by Ferriscan can be found in the Methods section of |
| |St. Pierre et al., 2005. |
| | |
| |A description of MR studies for determination of LIC by signal intensity ratio’s can be found in the |
| |Methods section of Gandon et al., 2004. |
|Participant |All ages |
|Source |Description of Quantification of Liver Iron by Magnetic Resonance Imaging (MRI) |
| |Wood, J. C., & Ghugre, N. (2008). Magnetic resonance imaging assessment of excess iron in thalassemia, |
| |sickle cell disease, and other iron overload diseases. Hemoglobin, 32(1-2), 85-96. |
| | |
| |Quantifying Liver Iron by MRI R2* |
| |Garbowski, M. W., Carpenter, J. P., Smith, G., Roughton, M., Alam, M. H., He, T., Pennell, D. J., & |
| |Porter, J. B. (2014). Biopsy-based calibration of T2* magnetic resonance for estimation of liver iron |
| |concentration and comparison with R2 Ferriscan. Journal of Cardiovascular Magnetic Resonance, 16, 40. |
| | |
| |St. Pierre, T. G., Clark, P. R., Chua-anusom, W., Fleming, A. J., Jeffrey, G. P., Olynyk, J. K., |
| |Pootrakul, P., Robins, E., & Lindeman, R. (2005). Noninvasive measurement and imaging of liver iron |
| |concentration using proton magnetic resonance. Blood, 105(2), 855-861. |
| |Gandon, Y., Olivie, D., Guyader, D., Aube, C., Oberti, F., Sebille, V., & Deugnier, Y. (2004). |
| |Non-invasive assessment of hepatic iron stores by MRI. Lancet, 363, 357-362. |
|Language of Source |English |
|Personnel and Training Required |A trained magnetic resonance imaging (MRI) technician is required to administer the MRI, and MRIs must |
| |be interpreted (“read”) by a trained radiologist, cardiologist, or other medical doctor. |
|Equipment Needs |A magnetic resonance imaging (MRI) machine at 1.5 Tesla and either |
| |a) Multiple-echo, gradient echo sequence for R2*/T2* evaluation, or |
| |b) Spin-echo sequence with a minimum echo time of 6 ms. |
|Protocol Type |Noncontrast magnetic resonance imaging (MRI) of the abdomen, CPT code 74181 |
|General References |Ghugre, N. R., Gonzalez-Gomez, I., Butensky, E., Noetzli, L., Fischer, R., Williams, R., Harmatz, P., |
| |Coates, T. D., & Wood, J. C. (2009). Patterns of hepatic iron distribution in patients with chronically |
| |transfused thalassemia and sickle cell disease. American Journal of Hematology, 84(8), 480-483. |
| |St. Pierre T. G., El-Beshlawy, A., Elaify, M., Al Jefri, A., Al Dir, K., Daar, S., Habr, D., |
| |Kriemier-Krahn, U., & Taher, A. (2014). Multicenter validation of spin-density projection assisted |
| |R2-MRI for the noninvasive measurement of liver iron concentration. Magnetic Resonance in Medicine, |
| |71(6), 2215-2223. |
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